1. Field of the Invention
The present invention relates to techniques for data management during backup of data between storage sub-systems.
2. Description of the Related Art
The technique of employing a remote computer is available as a technique for performing data copying between storage sub-systems.
The remote computer performs data copying through a network between a plurality of storage sub-systems in a physically remote location without interposition of a computer connected to the storage sub-systems.
With the remote computer technique, a duplicated condition of the shared storage region is always maintained between the storage sub-system that is the source of copying and the storage sub-system that is the target of the copying. Techniques relating to use of a remote computer are disclosed in U.S. Pat. No. 5,742,792.
In addition, the snapshot technique is available, in which a Point in Time Image is created of the storage region provided on the storage sub-system at a given point in time.
The image of the storage region created by the snapshot (hereinbelow termed the “snapshot volume”) is held independently of the original storage region. An image of the storage region is therefore held during creation of the snapshot. The snapshot technique is disclosed in U.S. Pat. No. 5,819,292.
NAS (Network Attached Storage), which is a storage sub-system connected to the network and that processes file-level access requests, is also available. NAS has a file system and can process access requests from a computer in respect of a file or directory.
There is a description of NAS at pages 54 and 55 of “Nikkei Electronics 6th Nov., 2000 (No. 782)” published by Nikkei BP Inc.